Question

Which term of ap 21 ,18, 15....... is -81

Answer 1

Answer:

Step-by-step explanation:

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Answer 2

$\huge{\underline{\underline{\red{\mathfrak{AnSwEr :}}}}}$

➠ Given :

First term (a) = 21

Common Difference (d) = -3

Last term (An) = -81.

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➠ To Find :

We have to tell that which term of the A. P is -81.

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➠ Solution :

We know that,

$\large{\boxed{\sf{A_n = a + (n - 1)d}}} \\ \\ \implies {\sf{-81 = 21 + (n - 1)-3}} \\ \\ \implies {\sf{-81 = 21 - 3n + 3}} \\ \\ \implies {\sf{-81 = 24 - 3n}} \\ \\ \implies {\sf{-81 - 24 = -3n}} \\ \\ \implies {\sf{-105 = -3n}} \\ \\ \implies {\sf{n = \dfrac{\cancel{-105}}{\cancel{-3}}}} \\ \\ \implies {\sf{n = 35}}$

$\sf{\therefore \: 35^{th} \: term \: of \: the \: A. P \: is \: -81.}$